1. Field of the Invention
The present invention relates to light sources utilizing arc tubes, and in particular, to an apparatus and method for connecting and disconnecting electrical power to a high intensity arc tube.
2. Problems in the Art
Many high powered lights utilize arc tubes as the light source. Arc tubes can create intense light from a relatively small package. Also, arc tubes can generate such light in a relatively efficient and a economical manner.
Substantial amounts of electricity are required, however, to generate light from arc tubes on the scale necessary for wide area lighting, for example. A side-effect of generation of light in this manner is also the generation of substantial amounts of heat. Therefore, two matters that must be addressed, with high intensity arc tubes are the danger presented to humans because of the amount of electrical power presented to arc tubes, as well as the high levels of heat that present not only as a danger to humans, but is potentially detrimental to the longevity of the electrical connections of the arc tube to the source of electricity for the arc tube.
Most arc tubes have a finite life span. Therefore, there are times when the arc tubes must be replaced in a fixture. Other times repair or maintenance on the fixtures requires opening of the fixture for interior access. On the other hand, because arc tubes must be replaced, fixtures generally have quick attach/detach mounts for each end of the arc tube to make replacement of the arc tubes quicker and easier.
Conventionally, short electrical leads are connected to the electrodes at each of an arc tube and an electrical connector is placed at the distal ends of the short leads. The electrical connector is many times an exposed electrically conducting component that can be screwed or otherwise mounted to another electrically conducting terminal that is connected to wiring that would then go to the electrical power source. Such exposed electrical connections represent a real and significant safety risk to persons working with such fixtures. If care is not taken, human contact to such surfaces could result in electrical shock. Still further, most of those connections are, because of the short electrical leads and space constraints inside the fixture, close to the ends of the arc tube or arc lamp inside the fixture. Therefore, the electrical connections and the leads must be able to withstand such heat over many hours of operation of the arc tube. They must therefore be made of special heat-handling materials. Also, during, and for a time after operation of the arc tube, the heat is such that any human working near the arc tube would also have the real and substantial danger of burn if they touched the arc tube.
Because some fixtures utilizing arc tubes, for example for sports lighting, are elevated on poles well above the ground, and at a location remote from any main power disconnect for electrical power to the fixtures, there is a risk that the worker will incorrectly assume the electrical power to the fixture has been turned off. There is no easy way to check the same and therefore the worker may risk going forward with opening the fixture when the electrical power is on and thus expose himself/herself to danger.
Still further, if the arc lamp has malfunctioned or no longer works for some reason, the worker may be misled to think that the power is off to the fixture because the light is not on or does not turn on. Again, such a mistake could risk serious consequences.
Some fixture manufacturers address this problem by including in the fixture hardware which automatically is intended to disconnect electrical power to the arc tube if the access opening to the fixture is opened. Essentially, if the access door is open, this system automatically breaks the electrical circuit to the arc tube. It therefore intends, in all cases, to remove electrical shock risk when a worker is working inside the fixture.
However, this does not address the problem of burns from the hot arc tube or the problem with failure of electrical connections that are placed near the ends of the arc tube, because of the heat generated from the arc tube. Still further, this adds complexity and cost to lighting fixtures. For example, conventional systems for automatic disconnect of electrical power to the arc tube utilize a switch or contactor. These components can individually cost on the order of $30 to $40 each. Also, there is the possibility that such components may fail or malfunction. Furthermore, such systems do not eliminate the requirement there still must be a manual connect and disconnect of the wiring to the arc tube at a position at or near the ends of the arc tube to replace the arc tube.
It has therefore been identified that there is a need in the art for a better solution to a way in which electrical power is connected and disconnected to an arc tube for a lighting fixture. It is therefore a principal object of the present invention to provide an apparatus and method which improves over or solves the problems and deficiencies in the art. Other objects of the invention include an apparatus and method which:
1. Provide a positive, fail-safe method of connecting and disconnecting electrical power to an arc tube.
2. Eliminates costs and weight by eliminating a need for automatic disconnect components.
3. Eliminates connection and disconnection of electrical power to the electrodes of an arc tube at a position at or near the electrodes of the arc tube.
4. Allows placement of the connection of electrical power to the arc tube at a position away from the arc tube and the heat generated from the arc tube.
5. Fosters a more durable electrical connection to electrical power.
6. Allows more economical and less complex materials to be used for the connections.
These and other objects, features, and advantages of the present invention will become more apparent with reference to the accompanying specification and claims.
The present invention is an apparatus and method for connecting and disconnecting electrical power to an arc tube inside a lighting fixture. The method includes mounting into a fixture an arc tube and connecting electrical power to leads to the electrodes of the arc tube at a position substantially spaced from the arc tube in the fixture. The apparatus of the invention includes an arc tube having first and second electrodes. Electrically insulated leads are connected to the electrodes and extend to distal ends. Connectors on the distal ends are connectable to complimentary connections of electrical power leads. The connectors and the electrical leads from the arc tube, including connections of the leads at the arc tube electrodes, are all insulated or shielded from direct human exposure to the electricity. The connections to electrical power therefore are not only at a location farther away from the arc tube and more remote in the fixture from the heat generated by the arc tube during operation, but also have no exposed parts to reduce the risk of electrical shock to a person connecting or disconnecting the leads, even if electrical power is on.